In the present study, we plan to examine changes in LDL receptor and HMG-CoA reductase mRNA concentrations during ezetimibe treatment. For comparison, effects of simvastatin and the combined administration of the two will be investigated. Since mRNA expression profiles provide information about effects at the transcriptional but not necessarily at the translational level, we will also analyze changes in the LDL receptor protein at the cell surface of mononuclear blood cells. As a functional marker for HMG-CoA reductase activity the ratio of serum lathosterol to cholesterol concentration will be used since it correlates with HMG-CoA reductase activity and serves also as a marker of total cholesterol synthesis.